Perceptual Modalities: The Overlooked Ecological Viewpoint.

I’ve just received the off-prints of a paper of mine being published in the Journal of Consciousness Studies on perceptual modalities, and what the enactive approach would have to say about the matter. Basically, I argue that there is a distinction between sensory modalities and perceptual modalities, with the latter being complex and structured not by physiological sensitivities but by skills. As a result, the ways in which we often break down our discussion of experience (into the visual, auditory and tactile components, for example) involves unnatural and problematic distinctions. I think taking this issue seriously gives us the means to argue against any simplistic relegation of the enactive approach to the “lower” forms of cognition (perception and bodily behaviour) while keeping the supposed “higher” forms of cognition (reasoning, decision making, problem solving [what are the differences between these things?]) as the province of more traditional, computational and representational viewpoints.

The paper was written some time ago, and I have since been introduced to (and am still becoming familiar with) ecological psychology and some of its various implications (my reviewers must have been as naive to Gibsonian thinking as I was). Ecological psychology is not really mentioned in the paper (Gibson is noted very briefly, but not in connection to the concept of perceptual modalities), and I now consider this an oversight I would like to correct, which is what this post is about (you might consider it an appendix to the paper itself).

In 1966 J.J. Gibson published The Senses Considered as Perceptual Systems. In that book Gibson argues that we should distinguish the senses, which provide the conscious qualities of experience, and perceptual systems, which enable us to explore and pick up information from the environment. (Note that this is not information as a representational or computational theorist would recognise it – it is action-relevant and specifies the relationship between an agent and its environment.) Perceptual systems are integrated sets of sensors and effectors by which the organism controls its interaction with information in the environment.

Perceptual systems are defined by what they do, rather than the set of sensors and effectors involved in them. Gibson (1966) identifies five perceptual systems (see p.50 of the book for a summary table):

The basic orienting system, which is involved with bodily equilibrium and is the means by which we pick up information about orientation to gravity, force and acceleration.

The auditory system, which picks up the nature and location of “vibratory events”.

The haptic system, allows for a variety of different kinds of exploration associated with the stretching and deformation of tissues, giving access to information about shapes, encounters with objects, solidity or viscosity and contact with the ground.

The taste-smell system, which gives information about “nutritive and biochemical values.”

The visual system which through ambient light specifies all those aspects of the environment that can affect the structure and dynamics of the optical flowfield.

Perceptual systems are active, rather than passive. They enable exploration rather than simply reception, not just the pickup of information but also the changing or ending of that information pickup on the basis of movement and engagement with the flow of the information.

In his definition of perceptual systems, Gibson thus argued in 1966 for a distinction between sensory modalities and modes of perception in a manner somewhat similar to that in my own recent paper. Gibson suggests that it is the perceptual system that allows us to pick up knowledge from the world, while sensory modalities provide for the conscious qualities of that experience.

How does the ecological approach differ from the enactive?

There is one major difference between the ecological approach to perceptual systems as described above and the enactive approach I put forward in my JCS paper. The ecological psychology literature tends to have an emphasis on the general and the universal. The aim appears to be to describe species-typical behaviours, and generalities based on shared embodiment, body scale and other immediately measurable factors.

This focus on the general, I believe, has lead many researchers to overlook the malleability of such perceptual systems. In examining species-typical behaviour ecological research seems often to take the abilities of people as givens in the normal case – we perceive gaps as steppable over, objects as liftable or sittable on based on the “abilities” of the human being (this is true of a number of authors I’ve read, including the likes of Reed, 1996, and somewhat more surprisingly Chemero, 2009). But the abilities of the human being are never static, and never given. They are earned, over years of development and often over hard years of deliberate practice and study. Cognitive psychologists Craig Speelman and Kim Kirsner in their book Beyond the Learning Curve (2005) do a pretty good job of showing that just about everything human beings do (including things we take for granted such as vocabulary) follows a power law of improvement with practice and disimproves without practice. Abilities are rarely, if ever, static.

The ecological psychologist Harry Heft (1989, 2001) does explicitly examine the issue of changing abilities both in terms of development, but also in terms of skill and other transformations of ability (such as how our perceptions change when we get sick and get better). In doing so, I think Heft largely bridges the gap between the ecological and enactive approaches, and I have to say at this point I’d consider his Ecological Psychology in Context essential reading for anyone (but particularly psychologists) interested in the enactive approach. My paper was an attempt to understand the structure or nature of perceptual modalities in an enactive view, but I think it might equally, in retrospect, be an argument about what perceptual systems might be from the point of view Heft’s intentional theory of affordances.